The present invention relates to a laminating device, and especially to a gripper mechanism of a laminating device having a movable gripper bar for holding and transporting a film which is cut by a cutting mechanism to a given length and laminated onto a base. The present invention also relates to the process by which the laminating device performs.
Before bases, such as printed circuit boards, multi-layer films, metal plates or substrates having two-sided vapor-deposited and/or bonded metal films applied thereto, are laminated with a photoresist film, the latter is stretched free of folds on horizontally or vertically aligned suction plates of suction tables. The film is then cut to the desired shape which is necessary for a congruent lamination of the photoresist film onto the respective base.
Laminating devices are described in laid-open European Patent Application Nos. 0,040,842, 0,040,843 and 0,041,642, in which a substrate or a base is laminated on both sides with a dry resist by the application of pressure. The dry resist films are drawn off supply rolls, one of which is provided for each side of the base to be laminated. The base, for example, may be a printed circuit board. The base and resist films are then fed to a pair of laminating drums, through the nip of which the two dry resist films and the interposed base pass.
In U.S. patent application Ser. No. 740,831, a movable gripper bar, which is connected to a vacuum pump via a flexible vacuum line, is proposed for holding and transporting a photoresist film via the suction plate of a vacuum table. The gripper bar is connected to two guides, which are displaceable along guide rods with the aid of a drive chain. A strip-shaped section of the photoresist film is seized by the elevated gripper bar and transported downwardly. The photoresist film then covers an upper vacuum table, the nip of the laminating station and a lower vacuum table. The entire length of stretched photoresist film corresponds to the size of the board areas to be laminated. A vacuum is built up in both vacuum tables so that the photoresist film may be carried free of folds via the suction plates of the vacuum tables. As soon as the gripper bar has reached its end position, the vacuum tables remain subjected to suction air and the photoresist film thereby stays stretched free of folds on the suction plates of the vacuum tables. In the case of this proposed gripper mechanism, the gripper bar seizes the photoresist layer of the photoresist film. However, this seizure may lead to impressions on the photoresist layer caused by the vacuum to which the gripper bar is subjected. In addition, the mechanical effect of the gripper bar on the photoresist layer may lead to fine splinterings in the photoresist layer, if the latter is slightly embrittled by lengthy storage. Both the impressions made by the gripper bar in the photoresist layer and the splinterings of photoresist material obviously impair the quality of the photoresist layer.